This invention relates to forming a diffraction grating and, in particular, to using a laser to form a diffraction grating in an optical fiber.
Communication rates over optical fibers may be increased by using WDM to transmit multiple channels via a single optical fiber. The multiple channels may be simultaneously transmitted through the single optical fiber by modulating each input channel into a data stream at a separate wavelength.
Signals modulated at different wavelengths may be coupled to or from an optical fiber using diffraction gratings. A diffraction grating may be formed in an optical fiber by spatially modulating the index of refraction of the optical fiber according to a predetermined period corresponding to a predetermined wavelength.
The present invention provides a method and apparatus for forming a diffraction grating in an optical fiber. First and second ultrashort laser pulses are generated. The first and second ultrashort laser pulses are directed to intersect and form an interference pattern including periodic intensity variations in the optical fiber. The periodic intensity variations cause corresponding periodic changes in an index of refraction of the optical fiber.
According to an aspect of the present invention, the positioning of the first and second ultrashort pulses relative to each other, respective operating characteristics of the first and second ultrashort pulses, and composition of the optical fiber are configured to result in self-focusing of the first and second ultrashort pulses as they are transmitted through the optical fiber.
According to another aspect of the present invention, an optical fiber including a diffraction grating manufactured according to the present invention is provided.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.